title: Synthesis and characterization of optical and redox properties of bithiophene-functionalized diketopyrrolopyrrole chromophores.
abstract: A series of six new 2,2'-bithiophene-functionalized diketopyrrolopyrrole (DPP) dyes 7a-f bearing different electron-donating and electron-withdrawing substituents at the terminal thiophene units was synthesized by palladium-catalyzed cross-coupling reactions. The to date unknown diiodinated DPP 2 and the corresponding boronic ester derivative 3 could be prepared in high yields, and these are shown to be versatile building blocks for the synthesis of DPP-based molecular materials by Negishi, Stille, and Suzuki coupling. The influence of the peripheral substituents on the optical and electrochemical properties of the present series of DPP dyes 7a-f were investigated by UV/vis and steady-state fluorescence spectroscopy and cyclic voltammetry, revealing an appreciable effect on the electronic nature of these dyes. The diamino-substituted DPP derivative 7e exhibits a strong absorption band reaching in the near-infrared (NIR) region, which is a highly desirable feature for application in organic photovoltaics.
authors.affiliation: Universität Würzburg, Institut für Organische Chemie, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Bürckstümmer
authors.forename: Annike
authors.initials: A
authors.lastname: Weissenstein
authors.forename: David
authors.initials: D
authors.lastname: Bialas
authors.forename: Frank
authors.initials: F
authors.lastname: Würthner